A living shrimp includes a head and an adjacent body that includes the meat portion. The body is formed as a plurality (typically six) of interconnected segments. The tail of the shrimp is connected to the first segment, and the last segment is joined to the head at a region known as the thorax. The segments include a shell that surrounds and encloses the meat. The body and shell include a convex dorsal side, and a concave ventral side to which appendages known as swimmerettes are attached. A long vein, known as the sand vein, extends along the dorsal part of the body, just under the shell.
In a typical shrimp processing operation, the head and swimmerettes of the shrimp are removed, and the shell enclosing the body is then either cut and removed, or cut such that the consumer can readily remove the shell. Most commonly, the shell is cut along the dorsal surface during processing, so that the sand vein can also be removed. The removal of the head and swimmerettes, the deveining, and the shell cutting can either be done by hand, or by means of shrimp processing devices of suitable structure.
One known technique for deveining a shrimp is to make a small cut through the dorsal portion of the shell, and then remove the vein using a pin or similar instrument. However the vein often breaks during such a process, leaving a portion of the vein in place. In a second technique, the shrimp is cut along the full length of its dorsal body portion, and the vein removed either at the same time, or in a subsequent step. However, cutting along the full length of the shrimp's dorsal side causes the shrimp's body to expand and deform.